程序代码：

#include<iostream>
using namespace std;

int numArry[3]={0};
int main()
{
    int *pFn_2=&numArry[0];
    int *pFn_1=&numArry[1];
    int *pFn=&numArry[2];

    int a,b,n;
    cin>>a>>b>>n;
    a=a%7;
    b=b%7;
    while (a||b||n)
    {
        *pFn_2=1;
        *pFn_1=1;
        for(int i=2;i<n;i++)
        {
            *pFn=(a * (*pFn_1) + b * (*pFn_2))%7;

            int *tmp=pFn;
            pFn=pFn_2;
            pFn_2=pFn_1;
            pFn_1=tmp;
        }

        cout<<*pFn_1<<endl;

        cin>>a>>b>>n;
        a=a%7;
        b=b%7;
    }

    return 0;
}

程序代码：

#include<iostream>


class Node
{
public:
    Node();
    Node(int numValue,Node *nextNodeValue);
    ~Node();
    void setNum(int numValue){num=numValue;}
    void setNextNode(Node *nextNodeValue){nextNode=nextNodeValue;}
    int getNum(){return num;}
    Node* getNextNode(){return nextNode;}
private:
    int num;
    Node *nextNode;
};

Node::Node()
{
    nextNode=NULL;
    //num=0;
}

Node::Node(int numValue,Node *nextNodeValue)
{
    num=numValue;
    nextNode=nextNodeValue;
}

Node::~Node()
{
}




Node *checkCircle(Node *head,int tmp,Node *pFn_1);
using namespace std;
int main()
{
    int a,b,n;
    cin>>a>>b>>n;

    Node *pFn=new Node();
    Node *pFn_1=new Node(1,pFn);
    Node *pFn_2=new Node(1,pFn_1);
    Node *head=pFn_2;


    
    while (a||b||n)
    {
        pFn_2=head;
        pFn_1=pFn_2->getNextNode();
        pFn=pFn_1->getNextNode();
        pFn_2->setNum(1);
        pFn_1->setNum(1);

        int flag=0;
        for(int i=2;i<n;i++)
        {
            int tmp=(a * (pFn_1->getNum()) + b * (pFn_2->getNum()))%7;

            Node *tmpPNode=checkCircle(head,tmp,pFn_1);

            if(tmpPNode)
            {
                pFn->setNum(tmp);
                pFn->setNextNode(tmpPNode->getNextNode());

                tmpPNode=tmpPNode->getNextNode();
                int count=1;
                while(tmpPNode!=pFn)
                {
                    count++;
                    tmpPNode=tmpPNode->getNextNode();
                }

                //test code这段if根本不可能成立
                if(count==0)
                {
                    cout<<"test message."<<endl;

                    cout<<tmp<<endl;
                    flag=1;
                    break;
                }

                int j=(n-1-i)%count;
                while(j--)
                {
                    pFn=pFn->getNextNode();
                }
                cout<<pFn->getNum()<<endl;
                flag=1;
                break;
            }

            pFn->setNum(tmp);
            pFn->setNextNode(NULL);
            pFn_2=pFn_1;
            pFn_1=pFn;
            pFn=new Node();
            pFn_1->setNextNode(pFn);
        }

        if(flag==0)
        cout<<pFn_1->getNum()<<endl;

        cin>>a>>b>>n;
    }

    return 0;
}

Node *checkCircle(Node *head,int tmp,Node *pFn_1)
{
    Node *tmpHead=head;
    while(tmpHead!=pFn_1)
    {
        if((tmpHead->getNum())==(pFn_1->getNum()))
        {
            Node *tmpP=tmpHead->getNextNode();

            if((tmpP->getNum())==tmp)
            {
                return tmpP;
            }
        }
        tmpHead=tmpHead->getNextNode();
    }

    return NULL;
}